Scapholunate Dissociation (SLD) remains one of the most common, and unfortunately, difficult problems to treat in the wrist. SLD generally relates to a tearing or damage to the interosseus ligament that connects the scaphoid and the lunate bones together. This ligament is also known as the scapholunate ligament. SLD often leads to arthritis of the wrist joint characterized with disability and chronic pain. Multiple techniques and implants have been proposed to treat SLD, however the results have been unreliable and disadvantageous.
One prior device for attempting to treat SLD is a rotating screw that is configured to be inserted between the scaphoid and lunate. Each end of the screw is threaded while the body of the screw is smooth to allow for rotation. This configuration unfortunately only allows for a single plane rotation, but not any significant dorsal-volar or radio-ulnar movement that the normal joint possesses. Because the normal scapholunate joint allows for movement in all three planes, this prior art screw does not function as an adequate substitute. As a result of this limited motion design, and the fact that the entire screw is made of metal, the prior art screw tends to pull out of the bone, break after time, or permanently restrict wrist motion.
The above described device and other prior art devices also require the patient to wear a cast or splint for two to three months after the surgery. This long cast time can considerably limit the range of motion in the wrist, and the results can be permanent. Accordingly, an improved, standardized system and approach is needed that is easier for the operating surgeon to implement and has better results and reliability for the patient.
Accordingly, one object of the present invention is to provide more consistent and reliable assemblies and surgical techniques to treat SLD. An additional object is to provide an implant that includes the same, or similar, modulus of elasticity as bone. A further object is to provide implants that allow movement in three different planes (dorsal-volar, radio-ulnar, and rotational movement). Still a further object is to provide a system and method that can treat both acute and chronic cases of SLD in which the dissociation can still be reduced to an anatomical alignment. An additional object of the teachings herein is to provide a device and method that would reduce the time a patient needs to wear a cast after the surgery. A further object of the teachings herein is to provide devices and methods that allow the patient to have early motion between the carpal bones and the radius after the surgery, while still retaining a reliable repair that will improve the final functionality of the wrist.
The above-listed objects of the invention are intended to be non-limiting, as further objects and advantageous will be readily appreciated by those with skill in the art upon reading the teachings below.